I need to build up a vector of non-linear equations to be used in fsolve to solve it. But I should make each element of the vector in each loop iteration. How can I make up such a vector? In fact, I can not use cell array. How can I convert a cell array like {@(x) x(1)+x(2)^2; @(x) x(1)-2*(x(2))} into an array like @(x) [ x(1)+x(2)^2 ; x(1)-2*(x(2))]? Because I want to use fsolve to solve the system of non-linear equations.
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2 Answers
Use func2str to get the function definitions in string and use str2func to get the desired function, if A is the cell array containing the function handles:
B = strcat(regexprep(cellfun(@func2str, A, 'uni', 0), '^@\(x\)', ''), ';');
F = str2func(strcat('@(x) [', B{:}, ']'));
Now F contains the desired function handle.
1 Comment
Rody Oldenhuis
+1, but note that this only works when all variable names are identical and equal to '
x'.Why convert? Why not use something like
% Your cell array
Fs = {@(x) x(1)+x(2)^2; @(x) x(1)-2*x(2)};
% Just use cellfun
solution = fsolve(@(y) cellfun(@(x) x(y), Fs), [0 0])
2 Comments
Mohsen Nosratinia
This should work, but then
cellfun will be called for each evaluation and it has a performance penalty.Rody Oldenhuis
@MohsenNosratinia: true, but it comes at the benefit of being much simpler to implement and easier to modify when things change; your solution is specific to this particular problem, mine is more general. Also things like
@(~) (for constants or so) are not parsed correctly.